July 2009 Archives

Interpolating proficiency rates

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One of my research interests has been the geographic distribution of early student achievement at the school district-level. District-level outcomes apply to large areas that are often out of alignment with neighborhoods, cities, and counties where local information could benefit parents and local governments making early education decisions. Additionally, I suspect that learning outcomes vary spatially according to a stochastic process influenced only partially by district boundaries, which in the context of multilevel modeling might appear as autocorrelation among within-group errors or as spillovers resulting from the modifiable areal unit problem. Therefore, I have begun examining sub-district geographic distributions.


School level results go a long way towards providing local-level information, but what about early learning outcomes in between school locations, where children live? As shown in the map at right, school-level results can be used to interpolate outcomes between schools. Interpolation is the process of using known values at a set of locations to estimate unknown values at different locations. When estimating an unknown value, nearby known values are typically given more weight (i.e., made to be more influential) than distant known values. Interpolation may be thought of as a three-dimensional version of locally weighted scatterplot smoothing (LOWESS). LOWESS yields a line, while spatial interpolation yields a surface, both lacking an explicit functional form.

Click on the image to see a larger map created with the help of Finley and Banerjee's Multilevel B-spline Approximation (MBA) package.

Computer recovery

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My computer crashed a few days ago. I own a Lenovo T60 running Windows XP. The crash happened very suddenly, right in the middle of working on an AERA proposal. My battery gauge needs calibrating, so I probably just ran out of power. I plugged in, restarted, and was greeted by a blue screen saying,
Stop: c0000218 {Registry File Failure}
The registry cannot load the hive (file):
or its log or alternate.

This type of failure has been appropriately dubbed the "blue screen of death."

Microsoft's support page attributes the problem to corrupt registry files. Their solution requires a Windows XP startup disk, but Lenovo does not provide such a CD when you buy one of their computers. Lenovo instead supplies its Rescue and Recovery software, which allows the owner to restore the computer to its factory state or to a back up point if the owner has taken initiative to archive their operating system configuration. I regularly archive my files onto DVDs, but I had not archived my system. I didn't want to restore my computer to its factory state because re-installing all of my software would take a very long time.

I successfully recovered my computer without the Windows XP startup disk, so there's hope for those of you with running XP on a Lenovo (or another brand that provides a pre-installed rescue option in lieu of a startup CD). Here's how, with a second, functioning computer nearby:

  • I read Microsoft's poorly written blue screen of death support page. The Guided Help option was no help at all... it kept stalling out on the second computer.
  • I read this great entry posted by subtle on http://www.geekstogo.com/.
  • I installed Avira NTFS4DOS Personal on the second computer and used it to create a DOS boot disk. (Note that if you do not have Lenovo Rescue and Recovery, then you can use the boot disk and DOS commands to follow the steps below, but it may be more difficult because the file names will appear truncated in DOS.)
  • I used Lenovo Rescue and Recovery to copy the system, software, sam, security, and default files from c:\windows\repair\ to a USB flash drive.
  • I also copied recent registry snapshots to the flash drive. Those files are located in c:\system volume information\_restore{***}\RP##\snapshot\, where *** is a bunch of seemingly random letters and numbers and ## are numbers corresponding to the order of recent snapshots made. In DOS, the location will appear as c:\system~1\_restor~1\rp##\snapshot\. The registry files corresponding with system, software, sam, security, and default are named _REGISTRY_MACHINE_SYSTEM, _REGISTRY_USER_SYSTEM, _REGISTRY_MACHINE_SAM, _REGISTRY_MACHINE_SECURITY, and _REGISTRY_USER_.DEFAULT. The DOS dir command will list the dates when the registry files were last saved, which can help you decide which snapshot number to use (i.e., how many days back to revert).
  • I used DOS commands to overwrite the files named system, software, sam, security, and default in c:\windows\system32\config\ with those from c:\windows\repair\. (You may want to back up the config files first.) Then I re-started the computer and performed repairs with chkdsk and Rescue and Recovery, which resulted in another blue screen of death failure:
    System error: Lsass.exe
    When trying to update a password the return status indicates that the value provided as the current password is not correct.

    I was happy to see that message because it occured much later in the boot up process than the original failure. In other words, I could tell I was making progress.
  • I renamed the snapshot registry files on the flash drive from _REGISTRY_MACHINE_SYSTEM and so forth to their respective config names: system, software, sam, security, and default.
  • Returning to DOS, I overwrote (again) those files located in c:\windows\system32\config\ with the just-renamed registry snapshots, thereby restoring the computer's registry files to a point from a few days earlier.

It took many, many hours, but I was able to recover my computer using the steps above. I'm thankful for the DOS I learned in high school and for the tips and shareware provided freely on the internet. I could have avoided a lot of headache if I had just used Rescue and Recovery to perodically archive my system configuration. I will from now on.